Apoptosis is a highly orchestrated cell suicidal program required to maintain a balance between cell proliferation and cell death. Tumor necrosis factor-o_ (TNF), a pleotropic cytokine, plays an important role in immunesurveillance. The interaction of TNF with its receptors triggers activation of a family of cysteine proteases or caspases that are essential for the execution of cell death by apoptosis. The ability to evade cell death pathway is a critical event in cancer progression. Various pro- and antiapoptotic signal transduction pathways regulate activation of caspases by TNF. Protein kinase C (PKC), a family of serinelthreonine kinases, plays a critical role in growth factor signal transduction pathway. During our previous funding period, we have shown that novel PKC isozymes act as anti-apoptotic proteins to inhibit cell death by TNF. The abundance of novel PKCs, however, was not sufficient to explain cellular sensitivity/resistance to TNF. A deregulation in Akt/protein kinase B (PKB) signal transduction pathway has been associated with the genesis of several cancers, including breast cancer although the molecular mechanism(s) by which this signaling pathway contributes to breast cancer pathogenesis is incompletely understood. We hypothesize that the PKC signal transduction pathway cooperates with components of the phosphatidylinositol 3-kinase (PI3K) pathway, such as PKB to regulate cell survival and cell death. The overall objective of this grant proposal is to delineate how a deregulation in PI3K/PKB signaling pathway that exists in breast cancer cells influences anti-apoptotic signaling by PKCo The long- term objective is to develop strategies to intervene with these pathways to inhibit progression of breast cancer.